Various Twitter-related tools and plugins have been multiplying fast over since we did our big Twitter Toolbox and 8 awesome Firefox plugins for Twitter
3x3Links enhances the speed-dial experience known from Opera, Chrome and the Firefox extension by allowing you to take your start page with you, organize it your way and to use high-speed keyboard shortcuts.
"Save Money. Save the Environment. Tired of printing web pages only to find your printout is full of ads, empty space and other junk you don't want? PrintWhatYouLike is a free online editor that lets you format any web page for printing in seconds!"
I use a firefox addon called Aardvark and can vouch for the advantage of being able to trim your webpages on the fly, especially when removing advertising and other junk before preparing a page for students, keeping it child friendly.
"Privacy Badger is a browser add-on that stops advertisers and other third-party trackers from secretly tracking where you go and what pages you look at on the web. If an advertiser seems to be tracking you across multiple websites without your permission, Privacy Badger automatically blocks that advertiser from loading any more content in your browser. To the advertiser, it's like you suddenly disappeared."